1. Field of the Invention
The present invention relates generally to collecting information about moving subscribers by means of a mobile network.
2. Description of the Related Art
In general, it is known to use a mobile network for locating subscribers, but the mobile network can be used in new ways for localization. For example, the applicant's prior patent applications FI20012139 and FI20030086 describe new ways to utilize mobile networks. These two patent applications and the present application share the characteristic in which way certain basic features of the mobile networks are utilized for locating mobile subscribers.
Patent application FI20030086 discloses such basic terms of prior art that are relevant also for the invention of the present application, thus we refer to the said patent application as an information source for the basic terms.
The method described in patent application FI20030086 comprises the following steps. At first, messages belonging to a certain message set are collected from the areas of a mobile network in which a terminal communicates with the mobile network using messages of the message set. These areas are border areas that are situated between location areas of the mobile network. Depending on a statistical survey, or another analysis to be performed, the border areas may be, for example, such road stages on which velocities of vehicles are measured. In general, the border areas are areas through which mobile subscribers move to the areas interested in a survey, or from which users can move out. The number of different types of users can be calculated by detecting the users' movements in the border areas. If required, the velocities of the users can also be calculated. When a message includes a temporary subscriber identifier, it is used for fetching a subscriber identifier from a subscriber database or from the subscriber data stored in a memory. Lastly, initial data is formed using subscriber identifiers. A part of those subscriber identifiers may be from the collected messages and another part may be from the subscriber data. A single subscriber identifier may be, for example, an IMSI that includes the following information: an initial value disclosing a country, an initial value disclosing an operator, and an initial value disclosing a subscriber.
FIG. 1 shows ways to implement the system described in the patent application FI20030086, assuming that the system is constructed within a mobile communication system. In the first embodiment network elements, such as signal analyzers 151, are added to the mobile communication system. Traffic important for the invention, i.e. the traffic between base stations and base station controllers, is monitored by means of the added network elements. The signal analyzer 151 is preferably connected to the point P1 in order to monitor signal traffic which is led through a 2 Mb E1 cable from a base station to a base station controller. More than one signal line can be assigned to the same base station controller, for example, the point P2 in FIG. 1. Typically one signal analyzer monitors from eight to sixteen E1 connections, each of which can be connected to twelve transmitter/receiver units, i.e. TRXs, when using the GSM technique. The signal analyzer 151 may include a user interface for specifying necessary information and the messages to be monitored. When the signal analyzer 151 detects a message of a certain type on the basis of an identifier of the message, the signal analyzer collects said message and sends data in accordance with its definitions to the address of the predetermined calculating server 150. The address of said server may be, for example, an IP or another network address, and/or a port address. If the system is intended for calculating velocities of subscribers, the velocities can be stored in the traffic database 155.
Network elements, such as the signal analyzer 152, are used in the second embodiment of the system. They are connected to monitor at the location points P3 traffic between a base station controller and the exchange 103 or the VLR 102.
Network elements, such as base stations, base station controllers, exchanges, or a VLR, are changed in the third embodiment. These elements can send certain messages to the server in order to collect information needed for the localization process.
In the fourth embodiment known charging records, such as the CDR (Charging Data Record), are used in a new way. In this embodiment an exchange of a mobile network, e.g. an MSC, is adapted to write a charging record when a terminal is moved into and out of a certain location area. For example, when the terminal 101 detects that the LAI of a new cell differs from the LAI of the cell that had the best audibility a little while ago, the terminal informs the VLR 102 via the MSC 103. Then the MSC receives a Location Updating Request message sent by the terminal, writes a charging record, and sends the charging record, or at least a part of its data content 160 either directly or via a data storage unit to the calculating server 150. Depending on the equipment deliverer, the data content 160 may include identifier data, such as an IMSI. Because it is possible to listen to the radio interface, hostile parties may locate users of the mobile network without their knowledge. In order to avoid this, a pseudo identifier, i.e. Temporary Mobile Subscriber Identity (TMSI), is taken into use. The relation between the TMSI and IMSI is stored in the VLR and in the mobile phone.
The above-described embodiments are related to the following drawbacks.
First, borders of location areas are not necessarily situated in the areas where movements of subscribers interested in a statistical survey are happening. This especially concerns the location area defined by a Location Area Identifier (LAI) or a Location Area Code (LAC) identifier (a LAI includes a LAC together with a country identifier or an operator identifier). In the method of the patent application FI20030086 observations about users are usually obtained, for example, when a location area (LAC) of a subscriber and a TMSI of the subscriber change.
Secondly, use of TMSI identifiers for locating subscribers cause VLR requests which load the mobile network.
Thirdly, the successful use of the TMSI identifiers requires that, if needed, the IMSI identifiers related to the TMSI identifiers can be fetched from a network of another mobile operator. It is possible that the other mobile operator is not co-operative in this matter, or the fetching of the IMSI identifiers becomes too expensive.
Fourthly, even use of TMSIs for the localization may be problematic because of data privacy and data security.